Brazilian Air Force personnel unload the corpse of one of the passengers of Air France flight 0447

Brazil's Air Force unloads the body of one of the victims recovered from the sea

"It will change zone each day and no time limit has been set."

The Emeraude is to be joined in the area by the Mistral, a naval command and control vessel equipped with helicopters.

French officials acknowledge the search will not be easy - the black boxes are thought to be in waters up to 3.7 miles deep.

If the Emeraude does locate the signal, the French scientific research vessel Pourquoi Pas will launch a mini-submarine to retrieve the recorders.